From some time the NPSI had actually two leaderships, elected in two separate congresses: on 24 June Stefano Caldoro was elected secretary of the right-wing faction of the party, while on 7–8 July Mauro Del Bue was elected secretary and De Michelis president by those NPSI members who wanted to take part to the foundation of the Socialist Party, whose first meeting took place on 14 July. In practical terms, there were two parties with the same name. After the split, both groups had a member in the Chamber of Deputies: Mauro Del Bue for the NPSI–De Michelis and Barani for the NPSI–Caldoro.

After a consensual separation, the group of De Michelis changed name into "Socialist Party" (coherently with name of the future party). Subsequently, in October, the two MEPs elected with the NPSI in 2004, De Michelis and Alessandro Battilocchio, joined the Socialist Group in the European Parliament. Since that moment the only NPSI was that led by Caldoro, who announced that its party was interested in joining The People of Freedom (PdL) along with Forza Italia and National Alliance.

From some time the NPSI had actually two leaderships, elected in two separate congresses: on 24 June Stefano Caldoro was elected secretary of the right-wing faction of the party, while on 7–8 July Mauro Del Bue was elected secretary and De Michelis president by those NPSI members who wanted to take part to the foundation of the Socialist Party, whose first meeting took place on 14 July. In practice, there were two parties with the same name.

United Socialists for Europe () was an electoral list for the 2004 European Parliament election composed of the New Italian Socialist Party (NPSI) of Gianni De Michelis and Socialist Unity (US) of Claudio Signorile.

CCL supports Ethernet and Token Ring local area network (LAN) connectivity directly, and other connectivity through a DLSw router. X.25 requires IBM's NPSI software plus a third party package. CCL does not support Bisync or start-stop.

In 2005 he became responsible director for the political newspaper La Discussione. In the 2006 general election Catone was elected in the Chamber of Deputies into the Forza Italia list and he joined the DCA-NPSI group.